Practical
reasoning in a modular mind

Peter Carruthers

Abstract: This paper starts from an assumption defended in the
author’s previous work. This is that distinctively-human flexible and creative theoretical
thinking can be explained in terms of the interactions of a variety of modular
systems, with the addition of just a few a-modular components and dispositions.
On the basis of that assumption it is argued that distinctively human practical
reasoning, too, can be understood in modular terms. The upshot is that there is
nothing in the human psyche that requires any significant retreat from a thesis
of massively modular mental organization.

1Introduction

Can we explain, or make sense of, distinctively-human practical reasoning
within a modular mental architecture? The question is worth asking, since there
are good reasons for thinking that the human mind is massively modular in its
organization. First, there is comparative, developmental, and
neuro-pathological evidence that this is so (Shallice, 1988; Gallistel, 1990;
Sperber et al., 1995; Tager-Flusberg, 1999). Second, there are strong
evolutionary and biological arguments for the conclusion that we should expect
the mind to be modular (Tooby and Cosmides, 1992). And third (and most
importantly), minds must be modularly organized if they are to be
computationally realized, since computations have to be modular if they are to
be tractable (Fodor, 1983, 2000; Bryson, 2000; McDermott, 2001). Since the
computationalist assumption is easily our best (and perhaps our only) hope for
understanding how minds can be realized in physical brains (Rey, 1997), this
gives us a powerful motive for believing in massive modularity. Rather than
giving up on computational psychology for the foreseeable future (as Fodor, 2000,
urges us to do in the light of the alleged ‘holism’ of the mental), we should
see just how far we can get in developing and defending the modularity
hypothesis.

This paper is the second stage in a two-part
investigation. In the first set of installments (Carruthers, 2002a, 2002b,
2003b) I investigated the extent to which we can make sense of
distinctively-human theoretical thinking in modular terms, arguing -
albeit tentatively and speculatively - for a positive outcome.
(I shall return to sketch some of the ingredients of that account below.) In
the present discussion I turn to consider our capacity for practical
reasoning, arguing that it, too, can be understood in terms of the interaction
of a number of modular systems, together with a minimum in the way of further
a-modular apparatus.

1.1On modularity

An initial
problem that arises for any attempt to explain practical reasoning in modular
terms is easily dealt with. This is the objection that practical reasoning
can’t be modular, because if an organism possesses just a single practical
reasoning system (as opposed distinct systems for distinct domains), then such
a system obviously can’t be domain-specific in its input-conditions. For it
will have to be capable of receiving as input beliefs and desires concerning
all of the various domains that the animal is capable of representing and
taking account of in its practical reasoning. Such a system could,
nevertheless, be highly restricted in terms of its processing data-base,
however; and this is all that is actually needed to secure its modular status
in the sense that matters (Sperber, 2002; Carruthers, 2003a). Let me elaborate.

Those who believe in
cognitive modules are apt to characterize them as domain-specific systems
of a certain sort. And developmental psychologists, too, are now united in
claiming (in contrast with the earlier views of Piaget and his followers) that
human development is domain-specific rather than domain-general in character.
This coincidence in terminology is unfortunate, and has encouraged a mistaken
reading of the sense in which modules are necessarily domain-specific. When
developmental psychologists talk about domains, they have in mind a domain of
facts of a certain kind, or a certain class of contents. Thus mind-reading is a
domain (dealing with the mental states of conspecifics), folk-physics is a
domain (dealing with the mechanical properties of middle-sized objects and
substances), folk-biology is a domain (dealing with generic relationships
amongst living things), and so on. And modularists believe, indeed, that each
these early emerging competencies is underpinned by a distinct cognitive
module. But this is by no means essential to modularity as such.

The best way to understand
the notion of modularity is by looking at the main arguments that have been
offered in support of modular accounts of mind (Carruthers, 2003b, 2004). A
module will be whatever those arguments would warrant. When we adopt this
perspective, what we get is that a module is a processing system which may be
innate or innately channeled in its development, which is targeted on some
specific adaptive problem (its domain), and which is encapsulated in
its processing from most of the information contained elsewhere in the mind
/ brain (thus enabling its operations to be computationally tractable).
Sometimes the adaptive problem in question will correspond to a domain in the
developmental psychologist’s sense, such as mind-reading or folk-biology. But
often it will not. And certainly there is nothing contradictory in the idea of
a module that can take all sorts of different kinds of content as input.[1]

1.2A very simple practical
reasoning system

Seen in this light, then, there is nothing incoherent in the idea of a
modular practical reasoning faculty. For example, we can imagine the following
very simple practical reasoning module (some non-human animals might have a
system of this sort). It takes as input whatever is the currently strongest
desire, P. It then initiates a search for beliefs of the form, Q É P,
cueing a search of memory for beliefs of this form and/or keying into action a
suite of belief-forming modules to attempt to generate beliefs of this form.
When it receives one, it checks its database to see whether Q is
something for which an existing motor-schema exists. And if so, it initiates a
search of the contents of current perception to see if the circumstances
required to bring about Q are actual (i.e. to see, not only whether Q
is something doable, but doable here and now). If so, it goes ahead and does
it. If not, it initiates a further search for beliefs of the form, R É Q,
or of the form Q (for if Q is something that is already happening
or about to happen, then the animal just has to wait in order to get what it
wants, it doesn’t need to do anything more); and so on. Perhaps the system also
has a simple stopping rule: if you have to go more than n number of
conditionals deep, stop and move on to the next strongest desire.

Although I described this practical reasoning module as
‘very simple’ (in relation to the sorts of reasoning of which humans are
capable), its algorithms would not, by any means, be computationally trivial
ones. Each of the component tasks, however, should be computationally tractable-
at least, so far as I can see. (Intuitions of computational tractability are
notoriously unreliable, however; so there is a promissory note here thateventually needs to be cashed.) And we know
that architectures of this sort are of very ancient ancestry.

The desert ant, for example, uses dead reckoning to
calculate the direction of a food source in relation to its nest (using
information about the time of day and year, and the angle of the sun in the
sky), and integrates that information with its current goals (to carry some
food home, or to return to a previously discovered food source) in order to
determine an appropriate course of action (Gallistel, 1990, 2000). Bees perform
similar calculations, and integrate the resulting information, not only with
their goals of returning to the hive or returning to a food source, but also
with the goal of communicating that information to other bees (Gould and Gould,
1995).[2]
There would therefore have been a very long period of time for computationally
sophisticated, but nevertheless relatively simple, systems of practical
reasoning to evolve (Carruthers, forthcoming).

Note that the sort of module described above would be
input-unrestricted. Since almost anything can in principle be the antecedent of
a conditional whose consequent is something desired (or whose consequent is the
antecedent of a further conditional whose consequent… etc.), any belief can in
principle be taken as input by the module. But what the module can do with
such inputs is, I am supposing, extremely limited. All it can do is the
practical reasoning equivalent of modus ponens (I wantP; if Q
thenP; Qis something I can do here-and-now; so
I’ll doQ), as well as collapsing conditionals (R É Q,
Q É
P, soR É P), and initiating searches for information of a
certain sort by other systems. It can’t even do conjunction of inputs, I am
supposing, let alone anything fancier.

We can easily imagine a minor elaboration of such a system
that would allow for the formation and execution of intentions for the future.[3]
When the system reaches a doable Q for which there isn’t presently an
opportunity, but where it is known that such opportunities often arise, or
where it is predictable that such an opportunity will arise, it then
stores the conclusion, ‘I’ll do Q’ in memory, together with some
specification of the conditions necessary to do Q (‘In circumstances C,
Q is doable’). Then it later reasons: Incircumstances C, Q is doable; circumstances C obtain;
so I’ll do Q (reactivating the previous decision). Again, the computations
involved are by no means trivial; but so far as I can see, they should be
computationally tractable ones.

Note that, as a result of the limited processing of which
the module is capable, there is a kind of de facto input-encapsulation
here too. For although the system can receive any arbitrary belief as input, it
can’t actually do anything with that input unless it is a conditional belief
with the right consequent, or a belief that is the antecedent of an existing
conditional (or a belief that the circumstances necessary for the truth of an
existing antecedent are likely to obtain in the future).

Would such a
system deserve to be called a ‘module’, despite its lack of
input-encapsulation? It seems to me plain that it would. For it could be a
dissociable system of the mind, selected for in evolution to fulfill a specific
function, genetically channeled in development, and with a distinct neural
realization. And because of its processing-encapsulation, its implementation
ought to be computationally tractable. In my view, this is all that any
reasonable notion of ‘modularity’ should require (Carruthers, 2003a, 2004).

1.3Can we get from there to here?

It is plain that human practical reasoning isn’t at all like this,
however. There seem to be no specific limits on the kinds of reasoning in which
we can engage while thinking about what to do. We can reason conjunctively,
disjunctively, to and from universal or existential claims, and so forth. And
contents from all of the various allegedly-modular content-domains can be
combined together in the course of such reasoning. This makes the practical
reasoning system look like an archetypal holistic, a-modular (and hence
computationally intractable) central system, of just the sort that Fodor
thinks makes the prospects for a worked-out computational psychology
exceedingly dim (Fodor, 1983, 2000).

However, I have already argued that seemingly a-modular
creative theoretical thinking can be constructed out of modular
components with minimal further additions (Carruthers, 2002a, 2002b, 2003b). On
the proposed account, a modular language faculty serves to link together the
outputs of various central / conceptual modules, and makes possible cycles of
processing activity by making non-domain-specific linguistic contents available
to the central modules once again, in ‘inner speech’ (Carruthers, 1998, 2002b;
Hermer-Vazquez et al., 1999; Spelke, 2002). A computationally-simple
supposition generator is built on the back of the language faculty, generating
new sentences in ways that pick up on weak similarities and analogies, past
associations, and so on (Carruthers, 2002a). And a sort of virtual faculty of
inference to the best explanation can be constructed from principles involved
in the assessment of linguistic testimony and the interpretation of speech, leading
to a preference for internally generated sentences that are consistent,
coherent, and fit the data, as well as being simple, fruitful, and unifying
(Carruthers, 2003b).

Might human practical reasoning, too, co-opt the resources
of this language-involving reasoning system? One fact that is especially
suggestive, in this regard, is our tendency to convert desiderative contents
into seemingly-descriptive ones. Thus instead of simply expressing a desire for
some object or situation (‘If only P!’, or ‘Would that P were the case!’), we
tend to say (and think) that P would be good, that P is important,
that I want P, or whatever. The main hypothesis to be explored, then, is
that by enabling motivational states to be re-represented as theoretical ones,
this tendency enables those states to be reasoned with using the
language-involving theoretical reasoning system. I shall return to this
suggestion in section 4 below.

2Pre-linguistic
practical reasoning

Let me back up a bit, however,
and first ask what further assumptions can be made about the nature and powers
of a modular practical reasoning faculty, prior to the advent of natural
language and the language-dependent supposition-generator. In addition to the
capacities described above - initiating searches for conditional beliefs about
actions that would lead to the satisfaction of desires, as well as being on the
look-out for circumstances that would activate previous decisions - what
other powers might it have had?

2.1Mental rehearsal

One thing that immediately-ancestral practical reasoning systems would
have had, surely, is the power to initiate episodes of mental rehearsal.
Once some sort of initial plan has been hit upon -I wantP; if
I do Q I’ll get P; Qis something I can do-
there would be considerable value in feeding the supposition that I do Q
back through the various conceptual modular systems once again as input, to see
if such an action would have other as-yet-unforeseen consequences, whether
beneficial or harmful. This doesn’t seem to require anything a-modular to be
built into the system yet; for both the desire for P, and the belief
that if Q then P, can be the product of individual modules.

What is presupposed here, however, is that the
representations in the practical reasoning system are in the right format for
use in generating inputs to the various central-modular conceptual systems.
This will be so if the practical reasoning system itself operates through the
manipulation of sensory images; or if it uses conceptual structures that can exploit
the same top-down systems deployed in the conceptualization of vision, in such
a way as to generate visual images with appropriate contents, that can then be
consumed by the central modules in the usual way. (I am assuming that nothing
here yet involves the generation of cross-domain contents; that is claimed to
depend on the activity of a language faculty and a language-dependent supposer,
to make their appearance rather later in evolution.) For such modules would, of
course, already have been set up in such a way as to feed off perceptual
outputs.

A good deal of the evidence
that has been cited – controversially – in support of chimpanzee theory of mind
can also be used -
much less controversially - to support the claim that this species of great ape, at
least, engages in mental rehearsal. (I am quite prepared to believe that there
is evidence of mental rehearsal from outside the great-ape lineage, too. But I
shall not pursue the point here.) For example: a subordinate ape knows the
location of some hidden food within an enclosure, and from previous experience
expects to be followed by a dominant who will then take the food. So the
subordinate heads off in the other direction and begins to dig. When the
dominant pushes her aside and takes over the spot, she doubles back and
retrieves and quickly eats the food.

Such examples are generally discussed as providing
evidence that chimps can engage in genuine (theory-of-mind involving) deception-
that is, as showing that the chimp is intending to induce a false belief in the
mind of another (Byrne and Whiten, 1988; Byrne, 1995) - whereas critics have
responded that chimpanzees may just be very smart behaviorists (Smith, 1996;
Povinelli, 2000). But either way, it seems that the chimp must engage in mental
rehearsal, predicting the effects of walking in the wrong direction and
beginning to dig (the dominant will follow and take over the digging), and
discerning the opportunities for hunger-satisfaction that will then be
afforded.

There is also direct evidence (of two distinct but related
kinds) of a capacity for mental rehearsal in hominids dating from at least
400,000 years ago, at a stage when the language faculty had presumably not yet
made its appearance. First, we know quite a bit about the cognitive requirements
of stone knapping, both from painstaking reconstructions of the sequence of
flakes (in those cases where not only a completed tool but also all the flakes
that were by-products of its production have been found), and from the direct
experience of contemporary knappers. And what we know is that stone knappers
have to plan several strikes ahead, preparing a striking platform and so on,
using variable and imperfectly predictable materials (Pelegrin, 1993; Mithen,
1996). Knapping cannot be routinized, and seems to require mental rehearsals of
the form, ‘If I hit it just so, then this will be the result; that
would then enable me to strike the result thus, which would give me the
desired edge’. The second source of knowledge is provided by the fine
three-dimensional symmetries that begin to be produced at about this time. Wynn
(1998) has argued convincingly that these require the knapper to visualize the
results of a planned strike, and then to rotate the image mentally in such a
way as to predict how the stone will then appear from the other side.

We know that members of these sub-species of Homo
were pretty smart, colonizing much of the globe and thriving even in sub-arctic
environments, while their brain-sizes approached the modern range (Mithen,
1996). And we can predict that their capacity for classifying items in the
world must have burgeoned at around this time. So it may be that it was the
increase in the number and sophistication of the concepts they employed that
strengthened the back-projecting neural pathways in the visual system, that are
used in normal vision to ‘ask questions’ of degraded or ambiguous input, and
that are also the source of visual imagery. (On the latter, see Kosslyn, 1994.)
In any case, whatever the explanation, we can be confident that these earlier
hominids were engaging in sophisticated forms of practical reasoning involving
mental rehearsal.

2.2Somasensory
monitoring

It is also presupposed by the account I am sketching, of course, that the
results of mental rehearsals can have further effects upon the practical
reasoning system, leading to strengthenings or weakenings of desire. But this
is very plausible. Besides engaging with the belief-generating modules,
imagined scenarios will engage with the appetitive system. Plausibly what
happens next, is that the animal should monitor its somasensory responses to
the imagined outcomes. All the animal then has to do is to monitor, not just
its reactions to the thought of the desired state of affairs, P, but
also to the various other states of affairs that it now foresees as
consequences of the plan to bring about Q. A very simple mechanism can
then be imagined that would sum across these various responses, either
diminishing or extinguishing the attractiveness of the original goal, or strengthening
it still further.

There is independent reason
the believe that monitoring our own emotional and bodily reactions to imagined
possibilities plays a crucial part in human practical reasoning. In the model
provided by Damasio (1994), for example, we convert theoretical judgments of
desirability into motivational ones by monitoring our own reactions to the
thought of the circumstance described. His frontally-damaged patients can
generally reason perfectly well on practical matters, making sensible considered
judgments about what ought to be done, and when. But they fail to act on those
judgments; and their lives as practical agents are a terrible mess. In
Damasio’s view, what has gone wrong is something to do with the somasensory
self-monitoring system. (See also Rolls, 1999, for a related theory.)

Here is how one might flesh out this account a bit in
modularist terms. Suppose that there are a whole suite of desire-generating as
well as belief-generating modular systems. The former have been designed to
take both perceptual and conceptual inputs of various sorts, combining them
with knowledge stored in module-specific data-bases, to generate appropriate
motivational states of varying strengths. When the supposition, ‘Suppose I do Q’
is received as input by these systems, they are keyed into action; and if Q
is itself something desirable, an appropriate desire, conditional on the
original supposition, will be generated. But the supposition that I do Q
is also taken as input by the various belief-forming modules, some of which may
generate further predictions of the form, Q É R. In which case R,
too, can in turn be taken as input by the desire-forming modules, issuing in
positive or negative (or neutral) motivational states, again still conditional
on the supposition that I do Q.

Essentially what one might have, then, in the absence of a
language faculty, are cycles of domain-specific activity which support
practical reasoning by mental rehearsal. We can imagine a variety of different
algorithms for integrating the motivational results of such reasoning. The
simplest would be summing the somasensory responses to the various
possibilities considered. But one can also easily imagine a variety of more
complex calculations, such as one in which a somasensory response is multiplied
by the number of predicted items to be gained (e.g. five yams as against two).[4]
And one can imagine a variety of ways in which considerations of time might be
factored into such calculations (e.g. discounting distant satisfactions to some
degree, or devaluing desires caused by currently perceived opportunities in
such a way as to compensate for the relative vividness of perception as against
mere imagination).

In what follows I shall be
supposing, then, that prior to the evolution of a modular language faculty we
might have had in place, both a capacity for mental rehearsal, and a
disposition to monitor our own responses to the predicted results of such
rehearsal, adjusting the level of our motivation to perform the action in
question accordingly.

3Adding
language and normative belief

It is then easy to see how things might go (and improve) when we add to
the whole arrangement both a natural-language faculty and a language-dependent supposer,
or supposition-generating system (Carruthers, 2002a, 2002b, 2003b). The latter
would vastly extend the range and creativeness of the suppositions whose
implementation can then be mentally rehearsed. And our reactions to those
predicted effects could still be monitored, and would still have a tendency to
create or diminish desires. We would be able to mentally rehearse scenarios
that link together concepts or propositions drawn from a variety of modular
domains, as well as genuinely-novel scenarios not inferable from previous
experience, but perhaps suggested by weak analogies or similarities from the
past, or from other domains.

I am suggesting, then, that we can come quite far in
approaching distinctively human practical reasoning within a basically modular
cognitive framework. There can be an encapsulated practical reasoning system
which draws its input from a variety of belief-producing and desire-producing
modules, and which can pass its output back as input to those modules once
again in the form of suppositions, for purposes of mental rehearsal. And once a
theoretical reasoning system is added to our cognitive architecture (consisting
inter alia of a language module and a language-dependent creative
supposition-generator), such mental rehearsals can become immeasurably more
flexible and creative.

3.1Weighing goals

All of the above has been concerned with reasoning about means,
however, not reasoning about ends. Cycles of mental rehearsal begin with
the supposition, ‘Suppose I did Q’, and adjust motivations and plans
accordingly. Yet humans don’t just reason in this fashion. We also
reason about ends. We reason about whether one end is better or more
important than another, which ends ought to be pursued in a given
context, and so forth. (And it is hardly very plausible that all of this should
really be covert reasoning about means, where the overarching end is happiness,
or maximum desire-satisfaction, or something of the kind.) How is such
reasoning about ends to be provided for within a modular framework, without
radically changing the powers of the practical reasoning system as such?

One obvious thing that humans can do in the course of
practical reasoning that hasn’t yet been allowed for in the simple model
sketched above, indeed, is to weigh one goal against another. Is there any way
in which a language-involving theoretical system could help with this? Well
yes, there is. One way in which theoretical thinking might help me to
adjudicate between the goal for P and the goal for G is by
enabling me to think in more detail about what getting each would involve, and
about their further consequences. Such thinking would provide me with more
detailed P-involving and G-involving scenarios to feed forward
through the appetitive system, and by monitoring my own reactions I can find
myself responding to one scenario more favorably than the other.

Another possibility would be this. Suppose that I have two
active goals in the present context, for P and for G. I can form
from these the quasi-descriptive thoughts (in language), ‘Getting P
would be good’ and ‘Getting G would be good’. I might then already have
a stored belief that enables me to adjudicate between them, of the form,
‘Getting P-type things is better than getting G-type things’. Or
I might believe things from which I can infer something that adjudicates
between them. (Such beliefs might be acquired by testimony from others,
inculcated by moral teaching, or learned from previous experience.) This would
then lead me to focus exclusively on the thought that getting P would be
good. Imagining P and monitoring my own reaction, the desire for P
is reactivated and now presented to practical reasoning as the only candidate
for action. The search for ways of achieving P can then go on as before.
Here the effects of theoretical thinking on practical reasoning would be by way
of manipulating attention.

We have made a start on our problem, then. But other
possibilities remain to be explored. One of these is that theoretical thinking
about norms can lead to the creation of a new desire.

3.2Normative modules

A number of the modules postulated by evolutionary psychologists (and to
some degree confirmed by later experimental work) are concerned with normative
issues. Thinking about permissions, obligations and prohibitions develops very
early in young children, for example (Cummins, 1996; Núňez and Harris,
1998).[5]
Moreover, they understand these notions, not just insofar as they pertain to
themselves (in which case one might have postulated some sort of direct
connection to the appetitive system or the will), but also as applying to third
parties. It seems inevitable, then, that we should think of the module in
question as delivering beliefsabout obligations and
prohibitions. But these would be beliefs that would be frequently accompanied
by the associated desires; and presumably the whole system would have been
designed in this way. So when I believe that I am obliged to do something, I
generally have a desire to do that thing in consequence. And when I believe
that I am forbidden from doing something, I generally have an accompanying
desire not to do that thing.

Similar points hold in connection with the
social-contracts system - or ‘cheater detection module’ - proposed and investigated
by Cosmides and Tooby (1992; Fiddick et al., 2000; Stone et al.,
2002). This, too, seems designed as a belief-generating module, which operates
not just in the first person, but also in the third person and from the
perspective of another (Gigerenzer and Hug, 1992). Its job is to reason about
social contracts in terms of cost / benefit structures, and in terms of who
owes what to whom; one central concept of the system being that of a cheat-
someone who takes the benefit in an exchange without paying the cost. And here,
too, it only really makes sense that such a system should evolve, if it were to
co-evolve with adaptations on the desiderative side of the mind, in such a way
that one generally also has a desire to do one’s bit in an agreed
exchange, as well as a desire to punish or avoid those who have cheated on a
contract (whether with oneself or with others).

From a modularist
perspective it seems likely, then, that we have one or more modules designed
for normative issues, which can straddle the belief / desire divide.[6]
It might be that such modular systems pre-existed the language module, or
co-evolved with it, or both. But the selection pressures that led to the
evolution of these systems would surely have been long-standing. We know that
exchange and trading networks long pre-existed the appearance of modern Homo
sapiens, for example, and we also know that these earlier hominids would
have led complex social lives, in which the co-ordination of plans and
activities would have been crucial (Mithen, 1996). Indeed, as Gibbard (1990
ch.4) emphasizes, it is problems of inter-personal co-ordination that create
the main pressure for systems of normative thinking and speaking to evolve.

Moral beliefs form one
sub-class of normative belief, of course. And a variety of different accounts
are possible of the relationship between moral thinking and the sorts of
modular systems envisaged above. On one view, for example, morality might have
an independent source, being grounded in our natural feelings of sympathy
when constrained by considerations of consistency (Singer, 1979). On another
view, morality might be what you get when you combine an idea drawn from one of
the above normative modules - that of fairness in an exchange - with
thinking about the general systems of rules that should regulate human conduct
(Rawls, 1972). And on yet another view, morality may result when more general
normative thinking is combined with a certain sort of distinctive affect
(Nichols, 2002). Moreover, once conducted in language, of course, or in cycles
of linguistically-formulated ‘inner speech’, such thinking would be capable of
uniting concepts across modular domains, as well as generating novel norms for
consideration and evaluation through the activity of the suppositional system.

I should emphasize that
the ideas sketched here are consistent with a variety of different positions
concerning the nature of moral belief itself. Some such account as this ought
to be acceptable to those who defend a sort of quasi-realism, or covert
expressivism, about moral discourse, say (Gibbard, 1990; Blackburn, 1993). But
it ought also to be acceptable to those who think that morality is more
properly cognitive in character, and who perhaps see moral truths as constructions,
grounded in the idea of a set of rules that no one could reasonably reject who
shared the aim of free and unforced general agreement, for example (Rawls,
1972, 1980; Scanlon, 1982, 1999).

4Theoretical
reasoning about desires and goods

The proposals on the table so
far, then, include first, a flexible and creative theoretical reasoning system
built out of modular components. (These would comprise a suite of
belief-generating and desire-generating conceptual modules, a language module
capable of integrating the outputs of the conceptual modules, a
supposition-generator built on the back of the language system, a disposition
to cycle natural language representations back through the whole arrangement,
in ‘inner speech’, as well as dispositions to accept such sentences under
conditions of ‘best explanation’.) And second, the proposal includes one or
more modules for generating normative beliefs, which can interact in complex
ways with the theoretical reasoning system, and which also tend to generate the
corresponding desires. So in these respects, at least, our theoretical thinking
can become practical.

This
cannot, by any means, be the whole story, however. For it is not just in
respect of moral matters, or with regard to obligations and prohibitions more
generally, that we are capable of practical reasoning of an unlimitedly
flexible and creative sort. We can also reason in the same kind of flexible and
creative way concerning things that we want. How is this to be
accommodated within a modularist perspective, without conceding the existence
of an a-modular, holistic, practical reasoning arena?

4.1The problem of descriptive goals

Let us return to the suggestion
briefly mooted at the end of section 1. This was that one way in which language
might be implicated in an enhanced (but still basically modular) practical
reasoning faculty, could result from our disposition to express desires and
intentions in descriptive form, thereby enabling them to be processed in the
manner of theoretical ones, and hence harnessing the resources of the
language-involving theoretical reasoning system. Thus instead of just thinking
longingly of some desired state of affairs, P, we are often disposed to
think in descriptive mode, ‘I want P’, or, ‘Getting P would be good’. These
thoughts are then in the right format to be treated by a flexible and creative
theoretical reasoning faculty. (See Gibbard, 1990 ch.5, for a related
proposal.)

One significant problem for such an account, however, is
the following. Systems of theoretical reasoning will be constructed so that conviction
is transferred from premises through to conclusions. If we start from initial
propositions that we believe to be true, and reason theoretically, then the
result will be a further proposition in whose truth we have some tendency to
believe. Now, the proposal under consideration here is that we can expand the
powers of our limited-channel practical reasoning module by being disposed to
convert motivational propositions into descriptive / theoretical ones, thereby
harnessing the non-domain-specific powers of our theoretical reasoning system.
But how are we to guarantee that transfer of conviction in an argument
involving such covertly-desiderative propositions will also deliver a transfer
of motivation?

Suppose that I start from some desired state of affairs, P.
I then transform this into the descriptive statement, P is good, reason
with it theoretically, and derive a further conclusion that I then have some
disposition to believe, Q is good. But what then ensures that I
translate this new descriptive belief back into a desire for Q?
Without such a ‘translation’, the augmenting of the practical reasoning module
by the resources of theoretical reason would be without any practical pay-off.

It looks, then,
as if my proposal for the use of non-domain-specific theoretical reasoning to
augment the powers of a limited-channel practical reasoning module might
require a corresponding adaptation to the practical reasoning system. Namely,
whenever the latter module receives a descriptive-evaluative, but covertly
desiderative, belief as input, it should generate the corresponding desire, and
reason accordingly. While such an adaptation is no doubt possible, it would
require a complex and messy interface between the two systems. For some way
would have to be devised of identifying, from amongst the wider class of
descriptive propositions, those that are covertly desiderative in content.
Given the extensive range of evaluative predicates humans employ, this would be
by no means easy. Moreover, such complexity would partly undermine the
attractiveness of the original proposal, which was to explain how human
practical reasoning can become non-domain-specific and inferentially flexible
by co-opting resources that are already available.

4.2Desiring to do what is best

More plausible, and more minimal, might be the following. We can
postulate that an adaptation subsequent to the appearance of
theoretically-augmented practical reason is an innate desire to do what one
judges that it would be best to do. For in that case, when I conclude my
theoretical reasoning about value with the belief that, all things considered,
doing Q would be best, then this would create in me the corresponding
desire to bring about Q.

We would still need a story about how such a desire could
be selected for, however. So we need a story about how the use of theoretical
reason to augment practical reason would have some advantages in the absence of
such a desire, and yet still more advantages with such a desire. Telling
such a story isn’t trivial, by any means. But we have already made a start on
it, in fact, through some of the proposals sketched in section 3.

Consider the attention-manipulating use of theoretical
reason, for example. One might expect that the effect of such attention
manipulation would be less than perfect. For often the original desire may
remain salient, and hence continue to intrude in the process of practical
reasoning. If our judgments of what is better than what are generally reliable
(aligning themselves with goals of greater adaptive significance), then there
might be pressure for the theoretical system to have yet more influence on the
practical one. An obvious way to do that, would be to fix in place an innate
desire to do what one judges to be the best.

Some such proposal can be rendered independently plausible
through its capacity to handle the traditional philosophical problem of
weakness of will. Sometimes we judge that, all things considered, it would be
best to do Q, but we then go and do P instead. How is this
possible? The answer comes readily to hand if a judgment of what it would be
best to do is a mere belief, albeit one that is innately liable to generate a
corresponding desire. For sometimes this tendency might fail; or the desire
created might be of insufficient strength to defeat the desire for P in
the competition to control the resources of the practical reasoning module.

4.3From the good to the
obligatory

There is another way in which theoretical reasoning about goods might
become practical. As we noted in section 3, a number of belief-forming modules
would seem to have -
associated with them or built into them - connections to desire, in
such a way that certain kinds of belief will normally give rise to a
corresponding desire. It is possible, therefore, that as our theoretical
reasoning abilities become enriched through the addition of language and
language-based creative thinking, thereafter some of the theoretical reasoning
that resulted could at the same time have become covertly practical,
piggy-backing on existing connections between belief-forming modules and
desire. To see how this can happen, we need to draw a distinction between the actual
and proper domains of a module (Sperber, 1996).

The proper domain of a module is the task or tasks
for which the system in question evolved. But the actual domain is the
set of concepts / conditions that happen to meet the modular system’s input
conditions. For example, the proper domain of the system in human males that
generates sexual desire from visual inputs would presumably have been the
presence of a sexually receptive female. But the actual domain now includes
paintings, photographs, videos, and much else besides.

In the case of the obligations / prohibitions module, the
proper domain would have been the task of learning, conforming to, enforcing,
and exploiting the norms that are prevalent in one’s society or social group.
But the actual domain might be much wider. So it could be that language enables
us to feed additional creative or inter-modular contents to the obligations /
prohibitions module, in such a way as to generate a desire out of a theoretical
belief where none existed previously. Specifically, if we were disposed to
convert evaluative statements of what it would be good to do into
statements of what one must do, what one is obliged to do, or of
what one should do, then this would meet the input-conditions of the
obligations / prohibitions module in such a way as to generate the appropriate
desire. And surely we do have just such a disposition. When reasoning about
what it would be good for me to do, and reaching the conclusion that doing P
would be best, it is entirely natural to frame such a conclusion in the format,
‘So that’s what I must do, then’, or in the thought, ‘So that’s what I should
do.’

A disposition of this sort would have the same sort of
evolutionary rationale as the previous proposal concerning a desire to do what
one judges best. For if our theoretical reasonings about value are reliable
enough in evolutionary terms, then one might expect pressure for an evolved
disposition to convert judgments of what it would be good to do or best
to do into judgments of what one must do. This would enable them to
harness the motivational powers of the normative reasoning system, in such away
-
again -
that our theoretical reasoning can become practical. And it would be the functional
equivalent of a disposition to desire what one judges to be best.

I begins to look, then, as if much that is distinctive of
human practical reasoning might be explicable in modular terms. Such reasoning
can happen via cycles of mental rehearsal and self-monitoring, and through a
disposition to cast practical issues in theoretical language, hence harnessing
the powers of our theoretical reasoning abilities (which are assumed, for these
purposes, to be themselves constituted out of a suite of interacting modules).
This would require the evolution of a further disposition, either to desire
what one judges to be best, or to convert theoretical judgments of value into
judgments of what one must do or is obliged to do -
hence piggy-backing on the simultaneous theoretical / practical functions of a
normative reasoning module - or both.

5Coda:
desires versus reasons

All of the above has been premised on the assumption that human practical
reasoning has a belief / desire structure, however. I have assumed that human
practical reasoning involves the integration of beliefs with desires to
generate intentions or actions. But some have argued that human theoretical
judgment can itself be directly practical. Some think that beliefs about what
it would be good to do are directly motivating, without requiring the
intervention of any desire (Dancy, 1993). Others have argued that it is our
perception of reasons for action, rather than our desires, that provides
the motivational element in practical reasoning - with desires themselves
only being motivating to the extent that they involve the perception that we
have a reason for acting (Scanlon, 1999).

This is not the place to
discuss such proposals in any detail. Let me just say that I regard them as
ill-motivated. The considerations that are alleged to support them do not, in
reality, do so (Brink, 1994; Copp and Sobel, 2002). And the authors of such
proposals display an unfortunate disregard for the constraints on theorizing
that should be provided by comparative and evolutionary psychology. Since we
have good reason to think that the minds of animals have a belief / desire
architecture, it ought to require some showing how a reasons architecture can
be grafted onto the back of, or in place of, that. And there should be discussion
of the evolutionary pressures that would have necessitated such wholesale
changes in our mental organization. Not only is none of this to be found in the
writings of the authors in question, but it is very hard to see how any such
story might go.

From the perspective that we have adopted in this paper,
of course, it is easy to see how someone might be tempted to think that beliefs
can be directly motivating. For all that need be manifest to me through
introspection is that I reach a theoretically-framed conclusion -
‘Doing P would be best, all things considered’ or ‘I ought to do P’
-
and then I act or form an intention to act. We aren’t normally aware of any
separate desire to do what is best, or to do what we ought. But such a desire
may be operative nonetheless. And something of this sort must be the
case if the basic belief / desire cognitive architecture that we share with the
rest of the animal kingdom is to be preserved.

6Conclusion

Massive modularity of mind is now
routinely assumed by just about everyone working in the artificial intelligence
community (Bryson, 2000; McDermott, 2001), and more generally amongst most of
those who have confronted the question of how intelligent functions can be
computationally realized. It is also assumed by many who come at the question
of human cognition from a biological, neurological, comparative-psychological,
or evolutionary-psychological perspective. But very few philosophers, and not
many developmental or cognitive psychologists, are inclined to think about the
architecture of the mind in such terms. I hypothesize that this is because the
distinctive flexibility and creativity of the human mind, which is manifest
both to ordinary introspection and to common sense, seems to resist explanation
within a massively modular framework (Fodor, 2000).

What I have done in this paper is to make a start on the
task of showing that distinctively human practical reasoning can be accounted
for within a modular mental architecture. (This is provided, of course, that I
am granted the assumption I have defended elsewhere, that distinctively human theoretical
thinking is consistent with massive modularity.) But this has only been a
beginning, and I have been able to provide only the merest sketch of an
account. I certainly don’t expect to have converted anyone to the modularist
cause. In fact, I shall be satisfied if I have only succeeded in convincing you
of the following: that it can’t any longer be taken to be a mere truism that
the human mind isn’t massively modular.[7]

Pelegrin, J. 1993. A framework for analyzing prehistoric
stone tool manufacture and a tentative application of some early stone
industries. In A. Berthelet and J. Chavaillon (eds.), The Use of Tools by Human and Non-human Primates, Oxford University
Press.

Stone, V., Cosmides, L., Tooby, J., Kroll, N. and Wright,
R. 2002. Selective impairment of reasoning about social exchange in a patient
with bilateral limbic system damage. Proceedings of the National Academy of
Science, 99, 11531-11536.

Wynn, T. 2000. Symmetry and the evolution of the modular
linguistic mind. In P. Carruthers and A. Chamberlain (eds.), Evolution and the Human Mind, Cambridge
University Press.

[1]
Sperber (1996) proposes, for example, that there is a dedicated logic module,
whose job is to derive some of the more accessible logical consequences from
any given set of beliefs as input. Such a system might be innate, and would be
focused on a specific adaptive problem: namely, how to derive some of the
useful logical consequences of what you already know. And it could be fully
encapsulated in its processing. For in order to derive Q from P
and P É
Q as inputs, such a system would need to consult no other beliefs
whatsoever.

[2]
Bees also integrate the information received from the dances of other bees with
an existing knowledge-base; sometimes to the extent of rejecting information
that they judge to be implausible. When one set of bees have been trained to
fly to a food-source on a boat in the middle of a lake, other bees reject the
information contained in their dances in favor of an indicated food-source that
is an equal distance away on the edge of the lake. And it isn’t that
bees are simply reluctant to fly over water, either. When the indicated food
source is on the other side of the lake, many bees will accept the information
and choose to fly to it (Gouldand
Gould, 1995).

[3]
Bratman (1987) argues convincingly that intentions aren’t reducible to
combinations of belief and desire; and he shows how the adaptive value of
intentions lies in the way that they facilitate planning in agents with limited
cognitive resources, by reducing the computational demands on decision-making.

[4]
We know that many species of animal can do approximate addition, subtraction
and multiplication; see Gallistel, 1990.

[5]
Núňez and Harris don’t believe in an obligations module themselves. But if
massively modular models of mind are taken for granted (in the way that I am
doing in this paper) then their work is quite naturally seen as providing
support for the existence of such a module.

[6]
I shall leave it open whether the social-contracts system is a sub-module
within a larger obligations / prohibitions system, or whether there are two
distinct modules here dealing with closely related types of content.

[7]
I am grateful to the following for discussion of earlier drafts of this
material: Patricia Greenspan, Scott James, and Christopher Morris.